Radio Frequency IDentification (RFID) can be used for locating and identifying objects. In this context, the RFID-systems are particularly useful for tracking of a large numbers of objects. These systems usually comprise RFID-readers and RFID-tags. When a power management system of an RFID-tag includes an energy storage device, e.g. a battery, then the tags are known as active tags. RFID-tags powered solely by the received RF-signals are called passive tags.
Intrasystem communication is typically conducted by an RFID-reader interrogating one or more RFID-tags by sending a Radio Frequency (RF) wave. In response, the tag that senses the interrogating RF-wave responds by transmitting back another RF-wave.
A significant challenge when designing RFID-readers is the correct detection of the response signal generated by the tags. Typically, the detection takes place in a detector that is part of a receiver module of the RFID-reader. Above challenge is at least in part caused by the greatly varying power value of the response RF-signal. Accordingly, the detector of the receiver module needs to have a stable threshold with respect to the power value of the incoming signal in order to distinguish relevant incoming RF-signals.
In this context, an inherent shortcoming of a typical IC-fabrication process for circuits being part of RFID-devices, typically manufactured using CMOS-technology, is the existence of a random variability of the physical parameters of the manufactured circuits. In particular, this mismatch, randomly affecting the parameters of equally designed and closely positioned circuit components, is difficult to mitigate and may significantly degrade the performance of the RFID-device as a whole and in particular the achieving of a stable threshold. A well-known method for fabrication mismatch mitigation is based on the assumption that the local variations average out as the area of the MOS-transistor increases, to scale the transistor size. However and in addition to increasing the area of the die, this usually reduces the bandwidth of the circuits and implies a higher circuit current in order to meet the performance specifications. A higher circuit current typically results in an increased power consumption in an RFID-device.